Bead Mill for Ceramic-Coated Battery Separator Slurry: A Safety Coating With a Narrow Window Ceramic-coated separators apply a thin layer of boehmite (AlOOH) or alumina (Al2O3) particles onto the polyethylene or polypropylene membrane that physically separates a lithium battery's cathode and anode, improving thermal stability and reducing short-circuit risk if the base membrane shrinks or melts.